What exactly can he do, I assume the track isnt copyrighted?
If it isnt its going to be hard to prove anything, and more than likely more time and hassle than its actually worth. He can harass the people that bit it and post in places stating that it was ripped off, it might make a dent in the biters reputation, but unless you go all out on a revenge vendetta you really aint going to make much difference. Id say call it a lesson learned and copyright your shit.
YOUR WORK HAS A COPYRIGHT ONCE IT'S CREATED. IF THEY'RE MAKING MONEY OFF HIS SHIT HE SHOULD GO AFTER THEM. LOOK AT THE NEXT PARAGRAPH FOR PROOF THAT HE'S IN FACT COVERED!
"If it doesn't have a copyright notice, it's not copyrighted." ?
This was true in the past, but today almost all major nations follow the Berne copyright convention. For example, in the USA, almost everything created privately and originally after April 1, 1989 is copyrighted and protected whether it has a notice or not. The default you should assume for other people's works is that they are copyrighted and may not be copied unless you know otherwise. There are some old works that lost protection without notice, but frankly you should not risk it unless you know for sure.
It is true that a notice strengthens the protection, by warning people, and by allowing one to get more and different damages, but it is not necessary. If it looks copyrighted, you should assume it is. This applies to pictures, too. You may not scan pictures from magazines and post them to the net, and if you come upon something unknown, you shouldn't post that either.
Threaten them bastards with a lawsuit and watch them back the fuck down! Tell them bastards to post an apology letter on sound click as well. Tell them they have 30 days to comply or you're going after them in court. They'll probably take everything they have down off of soundclick and break camp. Copy and paste the copyright law in your email or letter to them fucks. GAME OVER..U WIN!